Generation of digital lattice pattern under strongly focused light fields using Debye diffraction

Phase modulation can obtain the desired pattern by reshaping the light field in the focusing area of the objective lens, which has important application value in optical microscopic imaging, laser processing, optical tweezers and other fields.The traditional method is the GS algorithm (Gerchberg–Saxtonalgorithm). In the imaging system, GS algorithm can quickly calculate the phase distribution on the focal plane of the lens through the known intensity distribution of the Fourier domain. The GS algorithm is based on the paraxial approximation, and the phase distribution of the focal plane after the objective and the intensity distribution of the focal plane before the objective can be calculated by the Fourier Transformation (FT). However, in the case of objectives with high numerical aperture, FT cannot accurately describe the relationship between the phase distribution and the known light intensity distribution due to the strong depolarization effect, and can no longer accurately obtain the desired lattice pattern. To this end, based on Debye diffraction theory, this paper implements the generation of lattice patterns under a strongly focused light field. In order to calculate the phase distribution on the rear aperture of the objective lens and the light intensity distribution and phase information generated by the front focal plane of the objective lens, we replace the Fourier transform in the GS algorithm with the Debye diffraction integral. We used a digital pattern to verify the effectiveness of the method. The results show that the resulting lattice pattern is similar to the truth value, and the intensity of each point in the lattice is uniform. This method can realize the generation of arbitrary lattice patterns under the strongly focused light field, and further expand the use of light field modulation in biomedical optical imaging, laser processing, optical tweezers and other fields.